/*
 * Copyright (c) 2007 - 2020 by mod_tile contributors (see AUTHORS file)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; If not, see http://www.gnu.org/licenses/.
 */

/* Meta-tile optimised file storage
 *
 * Instead of storing each individual tile as a file,
 * bundle the 8x8 meta tile into a special meta-file.
 * This reduces the Inode usage and more efficient
 * utilisation of disk space.
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <utime.h>
#include <fcntl.h>
#include <assert.h>
#include <errno.h>
#include <pthread.h>

#include "store.h"
#include "metatile.h"
#include "render_config.h"
#include "store_file.h"
#include "store_file_utils.h"
#include "protocol.h"
#include "g_logger.h"


static time_t getPlanetTime(const char * tile_dir, const char * xmlname)
{
	struct stat st_stat;
	char filename[PATH_MAX];

	snprintf(filename, PATH_MAX - 1, "%s/%s%s", tile_dir, xmlname, PLANET_TIMESTAMP);

	if (stat(filename, &st_stat) < 0) {
		snprintf(filename, PATH_MAX - 1, "%s/%s", tile_dir, PLANET_TIMESTAMP);

		if (stat(filename, &st_stat) < 0) {
			// Make something up
			return time(NULL) - (3 * 24 * 60 * 60);
		}
	}

	return st_stat.st_mtime;
}

static int file_tile_read(struct storage_backend * store, const char *xmlconfig, const char *options, int x, int y, int z, char *buf, size_t sz, int * compressed, char * log_msg)
{

	char path[PATH_MAX];
	int meta_offset, fd;
	unsigned int pos;
	unsigned int header_len = sizeof(struct meta_layout) + METATILE * METATILE * sizeof(struct entry);
	struct meta_layout *m = (struct meta_layout *)malloc(header_len);
	size_t file_offset, tile_size;

	meta_offset = xyzo_to_meta(path, sizeof(path), store->storage_ctx, xmlconfig, options, x, y, z);

	fd = open(path, O_RDONLY);

	if (fd < 0) {
		snprintf(log_msg, PATH_MAX - 1, "Could not open metatile %s. Reason: %s\n", path, strerror(errno));
		free(m);
		return -1;
	}

	pos = 0;

	while (pos < header_len) {
		size_t len = header_len - pos;
		int got = read(fd, ((unsigned char *) m) + pos, len);

		if (got < 0) {
			snprintf(log_msg, PATH_MAX - 1, "Failed to read complete header for metatile %s Reason: %s\n", path, strerror(errno));
			close(fd);
			free(m);
			return -2;
		} else if (got > 0) {
			pos += got;
		} else {
			break;
		}
	}

	if (pos < header_len) {
		snprintf(log_msg, PATH_MAX - 1, "Meta file %s too small to contain header\n", path);
		close(fd);
		free(m);
		return -3;
	}

	if (memcmp(m->magic, META_MAGIC, strlen(META_MAGIC))) {
		if (memcmp(m->magic, META_MAGIC_COMPRESSED, strlen(META_MAGIC_COMPRESSED))) {
			snprintf(log_msg, PATH_MAX - 1, "Meta file %s header magic mismatch\n", path);
			close(fd);
			free(m);
			return -4;
		} else {
			*compressed = 1;
		}
	} else {
		*compressed = 0;
	}

	// Currently this code only works with fixed metatile sizes (due to xyz_to_meta above)
	if (m->count != (METATILE * METATILE)) {
		snprintf(log_msg, PATH_MAX - 1, "Meta file %s header bad count %d != %d\n", path, m->count, METATILE * METATILE);
		free(m);
		close(fd);
		return -5;
	}

	file_offset = m->index[meta_offset].offset;
	tile_size   = m->index[meta_offset].size;

	free(m);

	if (tile_size > sz) {
		snprintf(log_msg, PATH_MAX - 1, "Truncating tile %zd to fit buffer of %zd\n", tile_size, sz);
		tile_size = sz;
		close(fd);
		return -6;
	}

	if (lseek(fd, file_offset, SEEK_SET) < 0) {
		snprintf(log_msg, PATH_MAX - 1, "Meta file %s seek error: %s\n", path, strerror(errno));
		close(fd);
		return -7;
	}

	pos = 0;

	while (pos < tile_size) {
		size_t len = tile_size - pos;
		int got = read(fd, buf + pos, len);

		if (got < 0) {
			snprintf(log_msg, PATH_MAX - 1, "Failed to read data from file %s. Reason: %s\n", path, strerror(errno));
			close(fd);
			return -8;
		} else if (got > 0) {
			pos += got;
		} else {
			break;
		}
	}

	close(fd);
	return pos;
}

static struct stat_info file_tile_stat(struct storage_backend * store, const char *xmlconfig, const char *options, int x, int y, int z)
{
	struct stat_info tile_stat;
	struct stat st_stat;
	char meta_path[PATH_MAX];

	xyzo_to_meta(meta_path, sizeof(meta_path), (char *)(store->storage_ctx), xmlconfig, options, x, y, z);

	if (stat(meta_path, &st_stat)) {
		tile_stat.size = -1;
		tile_stat.mtime = 0;
		tile_stat.atime = 0;
		tile_stat.ctime = 0;
	} else {
		tile_stat.size = st_stat.st_size;
		tile_stat.mtime = st_stat.st_mtime;
		tile_stat.atime = st_stat.st_atime;
		tile_stat.ctime = st_stat.st_ctime;
	}

	if (tile_stat.mtime < getPlanetTime(store->storage_ctx, xmlconfig)) {
		tile_stat.expired = 1;
	} else {
		tile_stat.expired = 0;
	}

	return tile_stat;
}

static char * file_tile_storage_id(struct storage_backend * store, const char *xmlconfig, const char *options, int x, int y, int z, char * string)
{
	char meta_path[PATH_MAX];

	xyzo_to_meta(meta_path, sizeof(meta_path), (char *)(store->storage_ctx), xmlconfig, options, x, y, z);
	snprintf(string, PATH_MAX - 1, "file://%s", meta_path);
	return string;
}


static int file_metatile_write(struct storage_backend * store, const char *xmlconfig, const char *options, int x, int y, int z, const char *buf, int sz)
{
	int fd;
	char meta_path[PATH_MAX];
	char * tmp;
	int res;

	xyzo_to_meta(meta_path, sizeof(meta_path), (char *)(store->storage_ctx), xmlconfig, options, x, y, z);
	g_logger(G_LOG_LEVEL_DEBUG, "Creating and writing a metatile to %s", meta_path);

	tmp = malloc(sizeof(char) * strlen(meta_path) + 24);
	snprintf(tmp, strlen(meta_path) + 24, "%s.%lu", meta_path, pthread_self());

	if (mkdirp(tmp)) {
		free(tmp);
		return -1;
	}


	fd = open(tmp, O_WRONLY | O_TRUNC | O_CREAT, 0666);

	if (fd < 0) {
		g_logger(G_LOG_LEVEL_WARNING, "Error creating file %s: %s", meta_path, strerror(errno));
		free(tmp);
		return -1;
	}

	res = write(fd, buf, sz);

	if (res != sz) {
		g_logger(G_LOG_LEVEL_WARNING, "Error writing file %s: %s", meta_path, strerror(errno));
		close(fd);
		free(tmp);
		return -1;
	}

	close(fd);
	rename(tmp, meta_path);
	free(tmp);

	return sz;
}

static int file_metatile_delete(struct storage_backend * store, const char *xmlconfig, int x, int y, int z)
{
	char meta_path[PATH_MAX];

	//TODO: deal with options
	xyz_to_meta(meta_path, sizeof(meta_path), (char *)(store->storage_ctx), xmlconfig, x, y, z);
	g_logger(G_LOG_LEVEL_DEBUG, "Deleting metatile from %s", meta_path);
	return unlink(meta_path);
}

static int file_metatile_expire(struct storage_backend * store, const char *xmlconfig, int x, int y, int z)
{

	char name[PATH_MAX];
	struct stat s;
	static struct tm touchCalendar;
	struct utimbuf touchTime;

	//TODO: deal with options
	xyz_to_meta(name, sizeof(name), store->storage_ctx, xmlconfig, x, y, z);

	if (stat(name, &s) == 0) {// 0 is success
		// tile exists on disk; mark it as expired

		if (!gmtime_r(&(s.st_mtime), &touchCalendar)) {
			touchTime.modtime = 315558000;
		} else {
			if (touchCalendar.tm_year > 105) { // Tile hasn't already been marked as expired
				touchCalendar.tm_year -= 20; //Set back by 20 years, to keep the creation time as reference.
				touchTime.modtime = mktime(&touchCalendar);
			} else {
				touchTime.modtime = s.st_mtime;
			}
		}

		touchTime.actime = s.st_atime; // Don't modify atime, as that is used for tile cache purging

		if (-1 == utime(name, &touchTime)) {
			perror("modifying timestamp failed");
		}
	}

	return 0;
}

static int file_close_storage(struct storage_backend * store)
{
	free(store->storage_ctx);
	store->storage_ctx = NULL;
	return 0;
}

struct storage_backend * init_storage_file(const char * tile_dir)
{

	struct storage_backend * store = malloc(sizeof(struct storage_backend));

	if (store == NULL) {
		g_logger(G_LOG_LEVEL_ERROR, "init_storage_file: Failed to allocate memory for storage backend");
		return NULL;
	}

	store->storage_ctx = strdup(tile_dir);

	store->tile_read = &file_tile_read;
	store->tile_stat = &file_tile_stat;
	store->metatile_write = &file_metatile_write;
	store->metatile_delete = &file_metatile_delete;
	store->metatile_expire = &file_metatile_expire;
	store->tile_storage_id = &file_tile_storage_id;
	store->close_storage = &file_close_storage;

	return store;
}
